The present invention relates generally to multi-printer facilities of at least two imaging apparatus (such as printing or copying machines) and in particular, to liquid-toner replenishment systems for multi-printer facilities,
Liquid toner for imaging apparatus (such as printing or copying machines) generally contains carrier liquid, toner particles and a minute amount of charge director. Generally, each color of liquid toner is stored in a reservoir from which it is fed to a printing engine for developing images. For good quality printing, proper balance of the three liquid-toner components should be maintained within a narrow band. Depletion of the liquid-toner components is dependent on factors such as the number of prints, the percent of ink coverage of each image and other factors. However, these affect each component differently and each component of the liquid toner depletes at a different rate.
In some prior art systems, replenishment is carried out separately with respect to each component of the liquid toner.
Toner particles are generally replenished in the form of toner concentrate, having a relatively high percentage of particles in liquid carrier. In general, a measurement of the optical density of the liquid toner in the reservoir reveals that the concentration of toner particles has fallen below a predetermined level and that replenishment of toner particles is required.
Carrier liquid is added whenever the liquid toner level in the reservoir falls below a certain level.
Charge director may be added to the toner concentrate. Alternatively or additionally, it may be added to the carrier liquid. Alternatively or additionally, it may be supplied in a separate charge director solution. Charge director is added when the conductivity of the liquid toner is below a predetermined value.
In some systems toner concentrate is replenished from discrete replaceable cartridges, located within the imaging apparatus. Cartridge replacement involves machine down-time and operator attention. Both these factors are costly and inconvenient.
Automatic replenishment of toner concentrate, carrier liquid and charge directors are known.
U.S. Pat. No. 5,231,454, xe2x80x9cCharge Director Replenishment System and Method for a Liquid Toner Developing Apparatus,xe2x80x9d the disclosure of which is incorporated herein by reference, describes an automatic replenishment system for all three liquid toner components, for single, multicolor, imaging apparatus.
U.S. Pat. No. 4,860,924, xe2x80x9cLiquid Developer Charge Director Control,xe2x80x9d the disclosure of which is incorporated herein by reference, describes another system of automatic replenishment for all three components of the liquid toner, wherein again, the replenishment system is individual for single, multicolor, imaging apparatus.
U.S. Pat. No. 5,655,194 xe2x80x9cDispenser Apparatus Especially for Liquid Toner Concentrate,xe2x80x9d the disclosure of which is incorporated herein by reference, describes apparatus for dispensing liquid-toner concentrate and a container for the liquid-toner concentrate for single, multicolor, imaging apparatus. The system is further described in U.S. Pat. No. 5,558,900 xe2x80x9cLiquid Developer System,xe2x80x9d and U.S. Pat. No. 5,148,222 xe2x80x9cLiquid Developer System,xe2x80x9d the disclosures of which are incorporated herein by reference.
Other liquid developer assemblies are described in U.S. Pat. No. 5,557,376, the disclosure of which is incorporated herein by reference.
Exemplary forms of optical density measurement systems (to determine the need for replenishment of toner-concentrate) are shown in U.S. Pat. Nos. 4,579,253; 4,860,924; 5,793,490; and 5,570,193 the disclosures of all of which are incorporated herein by reference.
An exemplary form of conductivity measurement system (to determine the need for replenishment of charge-director solution) is shown in U.S. Pat. No. 4,860,924 the disclosure of which is incorporated herein by reference.
According to an aspect of some preferred embodiments of the present invention toner is replenished in individual imaging apparatus in a multi-printer facility from a central toner replenishment system.
In some preferred embodiments of the present invention, the central toner replenishment system comprises a central supply system for toner concentrate.
Preferably, where the multi-printer facility is single-color, the central supply system of toner concentrate comprises one tank of toner concentrate and each imaging apparatus has one liquid-toner reservoir. Preferably, where the multi-printer facility comprises multicolor imaging apparatus or a mixture of multicolor and single-color imaging apparatus, the central supply system of toner concentrate comprises as many as four and possible more tanks of toner concentrate, one for each color, and the multicolor imaging apparatus comprises as many as four and possibly more corresponding liquid-toner reservoirs each.
In some preferred embodiments of the present invention, each liquid-toner reservoir is replenished with toner concentrate directly from the central system. Alternatively, each liquid-toner reservoir comprises a toner-concentrate dispenser can which dispenses toner concentrate to the reservoir, on demand. Preferably, the toner-concentrate dispenser can is continuously replenished from the central system.
An aspect of some preferred embodiments of the present invention is that a multi-printer facility of at least two imaging apparatus comprises a central system of carrier liquid, supplying the individual imaging apparatus.
In preferred embodiments according to this aspect, the liquid-toner reservoirs of the imaging apparatus draw the carrier-liquid directly from the central system and have no carrier-liquid reservoirs. Alternatively, each imaging apparatus has its own carrier-liquid reservoir, which is replenished from the central system, on demand, when the level in the apparatus carrier-liquid reservoir falls below a given value.
In some preferred embodiments of the invention, the central system of carrier liquid supplies carrier liquid for cleaning purposes as well. In preferred embodiments, as described below, in which the individual imaging apparatus have no separate liquid-toner reservoirs, carrier liquid from the central system is supplied only for cleaning purposes.
An aspect of some preferred embodiments of the present invention is that a multi-printer facility of at least two imaging apparatus comprises a central liquid-toner system that supplies the liquid-toner working solution to the individual imaging apparatus, as required.
In preferred embodiments of this aspect, the imaging apparatus draw the liquid-toner working solution for each color directly from the central system and have no liquid toner reservoirs themselves.
Preferably, where the multi-printer facility comprises only single-color imaging apparatus, the central system comprises a single reservoir of liquid-toner working solution. Preferably, where the multi-printer facility comprises multicolor imaging apparatus or a mixture of multicolor and single-color imaging apparatus, the central system comprises as many as four or more reservoirs of liquid-toner working solutions, one for each color.
An aspect of some preferred embodiments of the present invention is that replenishment of charge director to a liquid-toner reservoir is made indirectly, on demand, by adding charge director to a carrier-liquid line just prior to replenishment of carrier liquid to a specific reservoir. This aspect is applicable to multi-printer facilities having central systems of liquid toner and carrier liquid as well as to facilities in which carrier liquid is supplied to each local liquid-toner reservoir from a local carrier liquid reservoir.
In preferred embodiments of this aspect, the carrier-liquid flow, for example, of the order of 50 milliliters per replenishment, is used to carry the charge-director, which is minute, for example, of the order of a few milliliters, from the carrier liquid line to the liquid toner reservoir. In addition to assuring that the proper amount of charge director reaches the reservoir, this method also purges the carrier liquid line so that no excess charge director is supplied to the reservoirs later.
There is thus provided, in accordance with a preferred embodiment of the invention, a multi-printer system comprising:
a plurality of imaging apparatus, each said apparatus comprising at least one liquid-toner reservoir, containing liquid toner;
a central source of toner concentrate;
a toner concentrate conduit which connects the central source to the individual imaging apparatus; and
at least one toner-concentrate pump which pumps the toner concentrate from the central source to the individual imaging apparatus.
In a preferred embodiment of the invention, the imaging apparatus each comprise:
a toner-concentrate dispenser which dispenses toner concentrate to said liquid-toner reservoir,
wherein the toner concentrate conduit connects the central source to the toner concentrate dispenser, such that toner concentrate is transferred from the central source to the toner concentrate dispenser via the toner concentrate conduit.
Preferably, the system comprises at least one controller.
Preferably, the toner concentrate dispenser comprises a dispenser can; and the can dispenses toner concentrate into the reservoir in response to a command from the at least one controller.
Preferably, the central source of toner concentrate comprises a central container of toner concentrate, containing a concentrate of the same color as a liquid-toner contained in a liquid-toner reservoir of the imaging apparatus; and the toner concentrate conduit is a branching feed line comprising: a junction having an input port and a plurality of output ports; a line connecting the source with the input port and a plurality of lines, each connecting one of the output ports with a different one of the imaging apparatus.
Preferably, a toner-concentrate pump is located on each line connecting the source with an input port. Preferably, the toner-concentrate pump operates continuously. Preferably, the at least one toner-concentrate pump comprises a high-viscosity pump.
In a preferred embodiment of the invention, in the imaging apparatus are multi-colored and the system comprises a plurality of central sources of toner concentrate, each having a different color of toner concentrate. Preferably, the plurality of liquid-toner reservoirs comprises liquid-toner reservoirs of at least yellow, magenta and cyan toner.
In a preferred embodiment of the invention, each liquid-toner reservoir comprises a particle density measurement device that measures a quantity related to the density of toner particles in the liquid toner and sends the measurements to the at least one controller and wherein the at least one controller transfers toner concentrate to the liquid toner reservoir responsive to the measurements.
Preferably, each of the printing apparatus includes:
a carrier-liquid reservoir from which carrier liquid is supplied to the liquid-toner reservoir; and
at least one local carrier liquid conduit through which carrier liquid is supplied to the liquid-toner reservoir, responsive to commands from the at least one controller; and the system includes:
a central source of carrier liquid; and
a central carrier liquid conduit which carries the carrier liquid to individual ones of the carrier liquid reservoirs responsive to commands from the at least one controller.
There is further provided, in accordance with a preferred embodiment of the invention, a multi-printer system comprising:
a plurality of imaging apparatus, each said apparatus comprising a liquid-toner reservoir;
a central source of carrier liquid;
at least one controller; and
a central carrier-liquid conduit which connects the central source of carrier liquid to each of the imaging apparatus and carries carrier liquid to the individual apparatus responsive to a command from the at least one controller.
Preferably, the imaging apparatus includes: a carrier-liquid reservoir from which carrier liquid is supplied to the liquid-toner reservoir, wherein the central carrier liquid conduit carries the carrier liquid to individual ones of the carrier liquid reservoirs responsive to commands from the at least one controller.
Preferably, the central carrier-liquid conduit comprises a branching carrier-liquid feed line, comprising: a proximal end at the central source of carrier liquid; and distal ends at the imaging apparatus.
Preferably, the branching carrier-liquid feed line comprises valves at its distal ends; and the valves are controlled by the at least one controller.
Preferably, the carrier-liquid conduit comprises a pump; and the pump is controlled by the at least one controller.
Preferably, each carrier-liquid reservoir comprises a carrier-liquid level indicator; and measurements of the carrier-liquid level indicator are sent to the at least one controller.
Preferably, each imaging apparatus comprises a conductivity measurement device that measures the conductivity of liquid toner in the liquid toner reservoir, and the system includes:
a source of charge director solution; and
at least one charge director solution conduit that communicates between the source of charge director solution and the at least one carrier liquid conduit, wherein a quantity of charge director solution is sent to the reservoir responsive to a low conductivity measurement.
There is further provided, in accordance with a preferred embodiment of the invention, a printer system comprising:
at least one liquid toner reservoir, each said reservoir including a first detector that provides a first signal when the amount of liquid toner therein falls below a given volume and a second detector that measures the conductivity of the liquid toner and produces a second signal responsive thereto;
a source of carrier liquid;
a source of charge director solution;
at least one controller;
at least one carrier liquid conduit that communicates between the source of carrier liquid and the at least one liquid toner reservoir;
at least one charge director solution conduit that communicates between the source of charge director solution and the at least one carrier liquid conduit,
wherein the controller is operative to transfer a first quantity of carrier liquid to a liquid toner reservoir via the charge director conduit when the first signal associated with the reservoir indicates a low volume condition for the reservoir and is operative to send a second quantity of charge director solution to the reservoir via the charge-director and carrier-liquid conduits, responsive to the second signal associated with the reservoir indicating a low conductivity condition.
Preferably, in transferring the charge director to the reservoir, the controller is operative to transfer the quantity of charge director solution to the local carrier conduit which charge director solution is then carried by a subsequent transfer of carrier liquid to the reservoir. Preferably, the controller is operative to send the charge director solution to the local carrier liquid conduit immediately prior to sending carrier liquid to the reservoir such that the carrier liquid carries the charge director into the reservoir.
In a preferred embodiment of the invention, the quantity of charge director solution sent to the liquid toner reservoir is substantially less than the quantity of carrier liquid sent to the reservoir.
Preferably, the charge director conduit joins the carrier liquid conduit near an entrance to the reservoir from the carrier liquid conduit.
There is further provided, in accordance with a preferred embodiment of the invention, a multi-printer system comprising:
a plurality of imaging apparatus, each said apparatus comprising:
a printing engine
a liquid-toner inlet line from which fresh liquid toner is fed to the printing engine;
a central source of liquid toner;
a liquid-toner feed which connects the central source to the liquid-toner inlet line;
at least one controller which transfers fresh liquid toner from the central source, via said feed.
Preferably, each imaging apparatus includes:
a liquid-toner exhaust line which collects discharged liquid toner from the printing engine and delivers it to the central source.
Preferably, the liquid-toner feed is a branching feed line comprising:
a junction;
a first feed line connecting the central source with the junction; and
a plurality of second feed lines connecting the junction with respective liquid-toner inlet lines of the imaging apparatus.
Preferably each of said plurality of feed lines includes a valve controlled by the at least one controller.
Preferably, the imaging apparatus are multi-colored; and a liquid-toner inlet line comprises a plurality of liquid-toner inlet lines.
Preferably, the central source of liquid toner is multi-colored, comprising a plurality of central containers of liquid toner of different colors. Preferably, the plurality of liquid-toner containers comprises liquid-toner containers of at least yellow, magenta and cyan toner.
In a preferred embodiment of the invention, the system includes:
a central source of carrier liquid; and
a carrier liquid conduit that connects the central source to the individual imaging apparatus, wherein the at least one controller is operative to transfer carrier liquid from the central source of carrier liquid to the individual imaging apparatus as required by the apparatus for cleaning.
Preferably, the system includes a carrier-liquid pump that pumps carrier-liquid to respective imaging apparatus responsive to commands from said at least one controller.
Preferably, the system includes a carrier liquid return conduit that collects carrier liquid after use by the imaging device and transfers it to the central source of carrier liquid.
Preferably, the system includes a separator that removes toner particles from the collected carrier liquid prior to its delivery to the central source of carrier liquid.
There is further provided, in accordance with a preferred embodiment of the invention, a multi-printer system comprising:
a plurality of imaging apparatus;
a central source of carrier liquid;
at least one controller;
a central carrier-liquid conduit which connects the central source of carrier liquid to each of the imaging apparatus and carries carrier liquid to the individual apparatus responsive to a command from the at least one controller.
Preferably, the system includes a carrier-liquid exhaust line which collects discharged carrier liquid from the imaging apparatus and returns it to the central source of carrier liquid.
Preferably, the imaging apparatus comprise electrostatographic imaging apparatus.
Preferably, the imaging apparatus comprise electrophotographic apparatus.
In a preferred embodiment of the invention, the imaging apparatus comprise printers. In a preferred embodiment of the invention, the imaging apparatus comprise copiers.
There is further provided, in accordance with a preferred embodiment of the invention, a method of dispensing toner concentrate in a multi-printer facility comprising a plurality of imaging apparatus, each said apparatus comprising a liquid toner reservoir, the method comprising:
providing a central source of toner concentrate; and
automatically transferring toner concentrate from said central source to individual imaging apparatus.
In a preferred embodiment of the invention, transferring comprises transferring toner concentrate directly to a liquid-toner reservoir of the individual imaging apparatus, in response to a deficiency of toner concentrate in the reservoir.
In a preferred embodiment of the invention, transferring comprises transferring toner concentrate to a liquid-toner concentrate dispenser associated with a liquid-toner reservoir in the individual imaging apparatus.
There is further provided, in accordance with a preferred embodiment of the invention, a method of providing liquid toner in a multi-printer facility comprising a plurality of imaging apparatus, comprising:
providing a central source of liquid toner; and
automatically transferring liquid toner from said central source to individual imaging apparatus in response to a need of liquid toner in said imaging apparatus.
There is further provided, in accordance with a preferred embodiment of the invention, a method of providing carrier liquid in a multi-printer facility comprising a plurality of imaging apparatus, comprising: providing a central source of carrier liquid; and automatically transferring carrier liquid from said central source to individual imaging apparatus in response to a need of carrier liquid in said imaging apparatus.